The invention relates generally to medication reconstitution and more particularly, to a compact device and method for storing and rapidly reconstituting dried medications.
Due to continued advances in genetic and cell engineering technologies, proteins known to exhibit various pharmacological actions in vivo are capable of production in large amounts for pharmaceutical applications. However, one of the most challenging tasks in the development of protein pharmaceuticals is to deal with the inherent physical and chemical instabilities of such proteins, especially in aqueous dosage forms. Pre-filled hypodermic syringes in which these protein pharmaceuticals and other medications are stored in aqueous form offer many efficiencies. However, many injectable medications degrade rapidly and lose their effectiveness in solution. Refrigeration and special packaging can increase shelf life, but add to cost, complicate storage, and offset many efficiencies provided by pre-filled syringes.
Because of the instability associated with the aqueous dosage forms, powder formulations are generally preferred to achieve sufficient stability for the desired shelf-life of a product. Various techniques to prepare dry powders are known and practiced in the pharmaceutical and biotechnology industry. Such techniques include lyophilization, spray-drying, spray-freeze drying, bulk crystallization, vacuum drying, and foam drying. Lyophilization (freeze-drying) is often a preferred method used to prepare dry powders (lyophilizates) containing proteins. Various methods of lyophilization are well known to those skilled in the art. The lyophilization apparatus and process applies a vacuum that converts liquid portions of a medication into a solid which is subject to a sub-atmospheric pressure to create a vapor. The vapor is drawn from the lyophilization chamber through vapor passages and exhausted to regions external of the lyophilizing apparatus. The lyophilizing process reduces the liquid medication to a dried powdery or granular form.
More particularly, freeze drying, or lyophilization, is a dehydration technique. It takes place while a product is in a frozen state (ice sublimation under a vacuum) and under a vacuum (drying by gentle heating). These conditions stabilize the product, and minimize oxidation and other degradative processes. The conditions of freeze drying permit running the process at low temperatures, therefore, thermally labile products can be preserved. Freeze drying has become an accepted method of processing heat sensitive products that require long term storage at temperatures above freezing.
Steps in freeze drying include pretreatment, freezing, primary drying and secondary drying. Pretreatment includes any method of treating the product prior to freezing. This may include concentrating the product, formulation revision (i.e., addition of components to increase stability and/or improve processing), decreasing a high vapor pressure solvent or increasing the surface area. Methods of pretreatment include: freeze concentration, solution phase concentration, and formulating specifically to preserve product appearance or to provide lyoprotection for reactive products.
The second step is to freeze the product. Freezing the product decreases chemical activity by decreasing molecular movement. Freezing is essentially the dehydration step in freeze drying; once the solvent matrix is in the solid (frozen) state, the solute matrix is “dry,” (although it may contain some amorphous water). A rule of thumb for freezing product is that the product container should preferably not be filled with product to more than half of its total volumetric rating. In practice this may also mean filling the product only to certain depth to facilitate freezing, ice sublimation and final water/solvent removal. This helps insure, in most cases, that the surface to depth ratio is such that freeze drying is not impeded by the product depth.
Once the product is at the end of its lyophilization cycle it should be removed from the freeze dryer. In a stoppering shelf/tray dryer, an inert gas may be bled into the chamber forming an inert “gas cap” over the product prior to stop. Many products are simply stoppered while under vacuum. The stoppers used most commonly on serum vials/bottles have a vacuum integrity of approximately five years when used in conjunction with tear off seals. Once the product is stoppered, the system is returned to atmospheric pressure and the lyophilizing shelves are unloaded.
Many devices presently exist in which lyophilized medication is stored in the chamber of a hypodermic syringe. Shortly prior to delivery to a patient, reconstitution is achieved by removing the tip cap from the syringe and placing the sharpened cannula of the syringe into a diluent container such as a vial, ampule, or any other rigid or flexible reservoir which could be engaged to the syringe. The plunger of the syringe is then pulled proximally to draw the diluent into the lyophilized medication chamber for mixing. The diluent reservoir is then removed and discarded. The diluent/powder solution in the syringe is then shaken sufficiently for complete mixing. Unless a sharpened cannula is already attached, one is mounted to the distal end of the syringe and the cannula is used to pierce the patient's skin at an injection site. The syringe plunger is then pushed into the syringe barrel to deliver the mixture to the patient. If necessary, the needle used for reconstitution of the lyophilized medication can be removed and replaced with a cannula more suitable for injection into a patient. An example of a system of this nature is that shown in U.S. Pat. No. 5,752,940 to Grimard.
More complex prior art includes hypodermic syringes made of glass or plastic having multiple chambers; in most cases two chambers. In one particular case, a chamber has a stopper slidably disposed at an intermediate position. A lyophilized medication is stored in the chamber distally located to the stopper, while a selected diluent is stored in the chamber proximally of the stopper. A plunger is slidably disposed in fluid-tight engagement with the chamber wall proximally of the diluent. Movement of the plunger in a distal direction urges both the diluent and the stopper toward the lyophilized medication. The stopper eventually will align with a bypass region formed in the syringe barrel, and further movement of the plunger will cause the diluent to flow through the bypass and into the distal portion of the chamber for fully mixing with the lyophilized medication. An example of a hypodermic syringe similar to the above is shown in U.S. Pat. No. 4,599,082 to Grimard.
The two-component hypodermic syringe assembly described above can function well; however, the need for two axially-spaced chambers along the body of the hypodermic syringe necessitates a longer syringe. In particular, the need for a chamber large enough to mix all of the diluent with all of the lyophilized medication before delivery to the patient dictates a space requirement that makes a container larger than if all the diluent and medication were not mixed before the delivery step. Since the lyophilizing process generally is carried out in the syringe, the lyophilizing apparatus must then be large enough to accommodate the longer syringe. Larger hypodermic syringes and correspondingly larger lyophilizing apparatus are more costly and require more space, which also increases cost.
Currently known devices and methods require thorough reconstitution and mixing of a lyophilized product into a diluent prior to injection, and can typically involve lengthy procedures (in excess of ten steps) in order to reconstitute a solid medication into a liquid formulation prior to administration. Such lengthy reconstitution steps can be complex, arduous, and tedious and may render injection of the lyophilized product unfeasible. Moreover, these complicated procedures present risks of foaming, contamination, and accidental needle pricks to the caregiver.
One of the most important aspects with the distribution of lyophilized product is the reliability of the container. Another important aspect is the control over costs of distribution. Devices used for pharmaceutical products must be disposable but at the same time, of high quality so that the patient is assured of accurately receiving the medication prescribed. Containers for lyophilized medical products should have a low cost, should be reliably usable, and should not negatively affect the shelf life of the product or its quality. Additionally the container should be easily and safely usable and intuitive to use. Containers having a large number of parts can be less reliable and more expensive to manufacture. Those with movable parts are more so.
By using a diluent from a separate vial or ampule, a separate space for a diluent is not required in the medication container, and it can be more compact. Thus, the syringe barrel can be substantially shorter than prior art two-component syringe assemblies, and a smaller lyophilizing apparatus also can be used. Even better is the use of blunt cannulas to conduct the diluent into the lyophilized medication. Providing a reconstitution container that does not include a movable plunger is even better for reliability and reduced cost.
In prior reconstitution devices and methods, the diluent is fully mixed with the lyophilized medication before delivery to the patient. In such fully mixed form, the concentration of the medication in the patient delivery is constant throughout the entire injection as is shown in FIG. 1 by line 30; i.e., there is no gradient. However, it has been found in some therapeutic settings that a gradient delivery of medication would be clinically beneficial to a patient. In particular, a higher concentration of the medication in the initial delivery tapering to a lower concentration during later delivery, as is shown in FIG. 2 by line 36, has been found to provide certain advantages. A device and method that provide such a concentration gradient delivery profile without any separate manipulation would be beneficial.
Hence those skilled in the art have recognized the need for an improved reconstitution device that facilitates lyophilization, storage, and the rapid reconstitution of dried medications. Another need has been recognized for a reduced size reconstitution device so that costs both in lyophilization and storage are reduced. Another recognized need is for the ability to reduce the number of steps in reconstitution of a dried medication. Reduction in manufacturing complexity and cost are also needs recognized by those of skill in the art. An additional need has been recognized for a device that controllably delivers with a gradient concentration. The present invention fulfills these needs and others.